1. Field of the Invention
The present invention relates to a light-emitting device, an electronic device, and a lighting device each using organic electroluminescence (hereinafter also referred to as EL).
2. Description of the Related Art
In recent years, research and development have been actively conducted on light-emitting elements utilizing organic EL (organic EL elements). In the fundamental structure of the organic EL element, a layer containing a light-emitting organic compound (EL layer) is sandwiched between a pair of electrodes.
Since the organic EL element is a self-luminous type, a light-emitting device including the organic EL element has advantages of high visibility, no necessity of a backlight, low power consumption, and the like. In addition, the light-emitting device including the organic EL element also has advantages that it can be thin and lightweight and it is highly responsive to input signals.
Furthermore, the light-emitting device including an organic EL element can achieve reduction in thickness and weight, and further have flexibility and high impact resistance; therefore, use of such a light-emitting element for a substrate having flexibility (a flexible substrate) has been proposed. The light-emitting element is applied not only to a light-emitting device but also to a semiconductor device or the like which operates by utilizing semiconductor characteristics.
For example, Patent Document 1 discloses a flexible active matrix light-emitting device in which an organic EL element or a transistor serving as a switching element is provided over a film substrate.
In addition, Patent Document 2 discloses an organic EL display device including, over a resin substrate formed of a flexible film, an organic EL display panel including an organic EL element, an inorganic barrier film covering a surface of the resin substrate, and a resin sealing film surrounding the organic EL display panel.
As a method for manufacturing a semiconductor device using a flexible substrate, a technique in which a semiconductor element such as a thin film transistor is formed over a base material such as a glass substrate or a quartz substrate, and then the semiconductor element is transferred from the base material to another base material (for example, a flexible base material) has been developed. In order to transfer the semiconductor element to another base material, a step for separating the semiconductor element from the base material that is used for forming the semiconductor element is necessary.
For example, in Patent Document 3, the following peeling technique using laser ablation is described. First, a separation layer formed of amorphous silicon is provided over a substrate, a layer to be peeled which includes a thin film element is formed over the separation layer, and the layer to be peeled is bonded to an object to which the layer to be peeled is transferred, by an adhesive layer. The separation layer is ablated by laser irradiation, so that separation is generated in the separation layer.
Furthermore, in Patent Document 1, a technique is described in which peeling is performed by physical force such as human hands. In Patent Document 1, a metal layer is formed between a substrate and an oxide layer and separation is generated at an interface between the oxide layer and the metal layer by utilizing weak bonding between the oxide layer and the metal layer at the interface, so that the layer to be separated and the substrate are separated from each other.